Autism is a lifelong debilitating developmental brain disorder characterized by impairments in social interaction and verbal/non-verbal communication. In a study of young adults with autism using brain imaging techniques (MRI diffusion tensor tracking (DTT)), researchers previously observed changes in white matter pathways involved in the recognition of faces and facial emotions (critical aspects of social interaction and non-verbal communication often affected in autism). To determine whether such changes are a fundamental abnormality that occurs early in infant development, DTT and new diffusion-sensitive MRI methods will be used to: 1) test for these pathway changes in infants at 20 high-risk for autism compared to 20 infants at low risk (where risk is based on the existence of an affected sibling), and 2) test for similar changes in language pathways in high-risk versus low-risk infants. Long-term goals of this research are to 1) provide a better understanding of the biological causes of autism, 2) improve the early diagnosis, screening, and treatment of autism, and 3) provide measures (biomarkers) of very early brain changes in autism that can be used to study the time relation between genetic, immunological, and environmental events (e.g., immunization) and the onset of measurable brain changes.